Heatpump Wiring Color Convention

Question

A heatpump thermostat is to be upgraded. I am unsure of:

1. Which color wire is the Common (thought to be BLUE)
2. Where should the brown wire be connected? (B node?)
3. Is the 'B' node in the photo associated with a color (BLUE? BROWN?)

I would like to be certain that I have connected the BLUE and BROWN wires correctly

Answer 1

This looks right to me as long as you have a two transformer system; separate power supplied for both heating and cooling. The common for this system must use the common from the cooling transformer. You clearly have the brown wire connected to the B terminal and the blue to the C. This is correct. The C terminal supplies power for the operation of the thermostat. The brown wire will be used to carry the signal in the event that the changeover valve is energized in the heating mode and the orange if in the cooling mode.